Bifurcated equilibria in centrifugally confined plasma

Journal Article · Mon Dec 15 04:00:00 EST 2008 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.2936924· OSTI ID:21259692

Shamim, I; Teodorescu, C; Guzdar, P N; Hassam, A B; Clary, R; Ellis, R; Lunsford, R ^[1]

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1. Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742 (United States)

A bifurcation theory and associated computational model are developed to account for abrupt transitions observed recently on the Maryland Centrifugal eXperiment (MCX) [R. F. Ellis et al. Phys. Plasmas 8, 2057 (2001)], a supersonically rotating magnetized plasma that relies on centrifugal forces to prevent thermal expansion of plasma along the magnetic field. The observed transitions are from a well-confined, high-rotation state (HR-mode) to a lower-rotation, lesser-confined state (O-mode). A two-dimensional time-dependent magnetohydrodynamics code is used to simulate the dynamical equilibrium states of the MCX configuration. In addition to the expected viscous drag on the core plasma rotation, a momentum loss term is added that models the friction of plasma on the enhanced level of neutrals expected in the vicinity of the insulators at the throats of the magnetic mirror geometry. At small values of the external rotation drive, the plasma is not well-centrifugally confined and hence experiences the drag from near the insulators. Beyond a critical value of the external drive, the system makes an abrupt transition to a well-centrifugally confined state in which the plasma has pulled away from the end insulator plates; more effective centrifugal confinement lowers the plasma mass near the insulators allowing runaway increases in the rotation speed. The well-confined steady state is reached when the external drive is balanced by only the viscosity of the core plasma. A clear hysteresis phenomenon is shown.

• OSTI ID: 21259692
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 12 Vol. 15; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
BIFURCATION
EQUILIBRIUM
HYSTERESIS
MAGNETIC MIRRORS
MAGNETOHYDRODYNAMICS
PLASMA
PLASMA CONFINEMENT
PLASMA SIMULATION
TWO-DIMENSIONAL CALCULATIONS